It is well known that fungal diseases caused by Helminthosporium species are particularly difficult to suppress by treating the seed of the cereal. The only successful treatment consists in using preparations containing organic mercury compounds as the active agent. However, since organic mercury compounds are toxic, it is desirable to replace them by non-toxic organic agents.
It has already been proposed to use 2-(thiocyanomethylthio)-benzothiazole in fungistatic compositions. It has also been proposed to use substituted benzimidazoles for the control of fungal diseases (French Patent Specification No. 105,412). This applies particularly to compounds of the formula ##STR1## wherein X is selected from the group consisting of hydrogen, halogen, alkyl groups containing 1 to 4 carbon atoms, a nitro group and alkoxy groups containing 1 to 4 carbon atoms; Y is selected from the group consisting of hydrogen, chlorine and bromine; R.sub.1 is selected from the group consisting of (i) alkyl groups containing 1 to 6 carbon atoms and such alkyl groups substituted with chlorine, bromine or a cyano group, (ii) alkenyl groups containing 3 to 6 carbon atoms, (iii) alkynyl groups containing 3 to 6 carbon atoms, (iv) benzyl, and (v) phenyl; and R.sub.2 is selected from the group consisting of hydrogen, alkyl groups containing 1 to 6 carbon atoms, and alkenyl groups containing 2 to 6 carbon atoms. Compounds falling within the foregoing definition are referred to hereinafter as "said substituted benzimidazoles". In practice the 1-(butylcarbamoyl)-2-benzimidazole carbamic acid methyl ester has proven to be particularly useful. Each of these agents is known to exhibit fungicidal activity. However, they do not have sufficient efficacy for maximum control of the Helminthosporium species.
It is an object of the present invention to provide fungistatic compositions which are more effective than those which could be obtained using each of the aforesaid compounds.